Another underdog option. Have a contest where to enter you pick a team or a few teams (it's more fun to have 3-5 teams to root for). For each win, you get 1 point times the seed. Have a preset range of discounts for the total points after the tourney. So if you pick an 7 seed and they win 3 games, you get 21 points. Pick a 3 seed and they win 4 games, you get 12. Maybe 12 gets you a 5% discount and 21 gets you 15%.